Technical Field
The present invention relates to an oxygenator module according to the preamble of claim 1 as well as an oxygenator according to the preamble of the coordinate apparatus claim as well as a production method according to the preamble of the coordinate method claim.
Description of the Related Art
Blood-gas exchangers or artificial lungs that are to replace or at least support the natural lung function temporarily or even long-term are referred to as oxygenators. Oxygenators are also used, for example, in the field of cardiac surgery as part of a heart-lung machine. A special field of application is the at least short-term treatment of acute lung failure. Oxygenators are used for patients, for example, who are treated, especially in an intensive care unit, with so-called extracorporeal membrane oxygenation (ECMO) to support the heart and/or the lungs. The most common type of oxygenator is the membrane oxygenator. Oxygenators are, for example, used for the delivery of oxygen to the blood and the absorption of carbon dioxide from the blood. For this purpose, an oxygen-rich gas, for example, can be guided through semipermeable, only gas-perfusable hollow fiber membranes around which blood flows. Similarly to the natural lung, the gas exchange in this process is based on diffusion, in particular due to a difference in concentration (a partial pressure difference) of oxygen or carbon dioxide in the blood and in the gas.
The hollow fiber membranes consist, for example, of a plurality of hollow fibers from microporous plastics, for example polypropylene or polymethylpentene, that are arranged in layers (in particular fiber mats). The individual hollow fibers have a length of 100 to 200 mm, for example, and are arranged at a distance of 0.1-0.2 mm, for instance. They can be connected with each another or knotted together by so-called warp threads. The fiber mats formed by a plurality of hollow fibers can be designed to be one or two layers. Plasma-tight hollow fibers with a closed outer layer (closed porous fibers, in particular polymethylpentene-based (PMP) fibers) or non-plasma-tight hollow fibers with a non-closed outer layer (continuously porous fibers, in particular polypropylene-based fibers) can be provided. Furthermore, a distinction is made between plasma-tight (in particular polypropylene-based) and highly porous, non-plasma-tight (in particular polymethylpentene-based) fibers. Plasma-tight fibers are preferably used for oxygenators that must be used for a longer period of time of, for example, 14 days, in particular up to 29 days, particularly for the ECMO. The hollow fibers are arranged in an oxygenator module of the oxygenator.
Disadvantageous in this respect is in particular in connection with extracorporeal lung support systems that the oxygenators mostly cannot be used for longer than a period of one month, particularly due to the risk of coagulation (so-called “clotting”), which reduces the gas exchange capacity. This risk exists primarily with low blood flows and/or oxygenators that are not uniformly passed through in consequence of their geometry. Low blood flows lie, for example, in the range of 0.5-1.5 L/min or below. The oxygenators are also no longer passed through uniformly, i.e., no longer with uniform flow rate, particularly with increased operating time, as coagulations form. Often, areas develop that are passed through only with lower than the optimum flow rate. This disadvantageously affects primarily the gas exchange capacity for oxygen (O2), whereas the gas exchange capacity for carbon dioxide (CO2) depends more on the gas flow than on the blood flow. Here, the risk of coagulation exists across areas in which blood stagnation or blood stasis occurs.
In order for the perfusion with blood to take place as uniformly as possible, it is known to arrange a blood distributor plate upstream of the hollow fibers in a housing of the oxygenator. The distributor plates have the task of areally spreading the blood flow. They can be designed, for example, as perforated, transparent plates that do not have any openings in the area of the incident blood stream. Furthermore, a cover of the housing can have a flow-guiding geometry in a blood inlet area and can define, especially with an angular housing, an inclined plane for compensating pressure differences. Here, distributor legs are also provided, by means of which an inflow can be adjusted, even though the inflow mostly does not occur in a uniform manner in this process.
Even the specific arrangement of the fibers in the oxygenator module can influence the gas exchange rate. Oxygenator modules are known in which the individual layers of hollow fibers are arranged one above the other and at the same time, the fibers in one of the layers are turned with respect to the fibers in an adjacent layer. The fibers can be turned by 90 degrees, for example, so that a cross-shaped arrangement results. Multiple layers then form a cross-shaped fiber bundle.
The oxygenator modules are mostly produced by fixing the hollow fibers in casting compound. In the process, the casting compound is introduced into a mold, in which the fiber layers are arranged, and is arranged on an inner sheath surface by eccentric rotation of the mold due to centrifugal forces and cures therein and forms a so-called potting. In doing so, this process step is repeated for several sides of the fiber bundle, in particular four times, until the fiber bundle is enclosed and fixed from all sides by the potting. Thus, a cavity can be formed by the potting in which the fibers are arranged in a liquid-tight manner with respect to the surrounding and blood, for example, can flow around the fibers. Thereafter, the potting is removed from the mold. On the mold, so-called casting caps are provided on all sides which can be removed after the casting in order to expose the fibers. In doing so, the mold can be formed by the later (top and bottom) covers of an oxygenator on the one hand and the casting caps on the other hand. The outer sheath surfaces of the potting can be reworked in order to expose the ends of the fibers and make them accessible for gas loading.
Disadvantageous in these oxygenator modules is the fact that they can only be produced in a relatively expensive manner and that in the process, edges, transition regions and gaps between the individual sections of the potting can often also not be avoided in the cavity formed by the potting. This results in dead spaces in which perfusion cannot occur in a uniform manner which increases the risk of coagulation and reduces the period of application of the oxygenator module. It is also disadvantageous that the required quantity of casting compound at the individual sides of the module is to be selected in different sizes in certain cases so that the respective work step with the individual sides cannot be adjusted exactly the same. Rather, manual precise adjustments are required, whereby additional sources of error and variations in quality cannot be ruled out.
The task of the present invention is to provide a better apparatus for gas exchange between a gas and the blood of a human, animal or separate organ, in particular for extracorporeal lung support systems, as well as a better method for producing such an apparatus.